WO2024116918A1

WO2024116918A1 - Liquid ejecting head and liquid ejecting device

Info

Publication number: WO2024116918A1
Application number: PCT/JP2023/041546
Authority: WO
Inventors: 直樹小林
Original assignee: 京セラ株式会社
Priority date: 2022-12-02
Filing date: 2023-11-17
Publication date: 2024-06-06

Abstract

This liquid ejecting head comprises a plurality of individual flow passages, a first common flow passage, a second common flow passage, a supply flow passage and a recovery flow passage. Each individual flow passage includes a pressurizing chamber, a first throttling portion between one end portion and the pressurizing chamber, and a second throttling portion between an other end portion and the pressurizing chamber. In each individual flow passage, the first common flow passage is connected to the one end portion, and the second common flow passage is connected to the other end portion. The supply flow passage is connected to the first common flow passage, and the recovery flow passage is connected to the second common flow passage. A combined flow passage resistance of the second common flow passage, the recovery flow passage and the first throttling portion is greater than a combined flow passage resistance of the first common flow passage, the supply flow passage and the second throttling portion.

Description

Liquid ejection head and liquid ejection device

The present invention relates to a liquid ejection head and a liquid ejection device equipped with the same.

　Liquid ejection devices equipped with a liquid ejection head are known (see, for example, Patent Document 1). The liquid ejection head includes a plurality of individual flow paths each having a nozzle with an ejection hole formed therein for ejecting liquid and a pressure chamber, a first common liquid chamber connected to a first connection portion of each of the plurality of individual flow paths, and a second common liquid chamber connected to a second connection portion of each of the plurality of individual flow paths. In the liquid ejection head, the first common liquid chamber functions as a flow path of a supply system that supplies liquid to each of the plurality of individual flow paths, and the second common liquid chamber functions as a flow path of a recovery system that recovers liquid that has not been ejected from the ejection hole in each of the plurality of individual flow paths.

JP 2020-138373 A

The object of the present invention is to provide a liquid ejection head capable of suppressing backflow of liquid from the recovery system flow path to an individual flow path while liquid is being ejected from the ejection hole, and a liquid ejection device equipped with the same.

A liquid ejection head according to one aspect of the present invention comprises a plurality of individual flow paths through which liquid flows, each having one end, another end, and an ejection hole disposed between the one end and the other end for ejecting liquid; a first common flow path having a first opening and connected to the one end of each of the individual flow paths; a second common flow path having a second opening and connected to the other end of each of the individual flow paths; a supply flow path having an inlet through which liquid flows in from the outside and connected to the first opening of the first common flow path and supplying the liquid flowing in from the inlet to the first common flow path through the first opening; and a recovery flow path having an outlet through which liquid flows out to the outside and connected to the second opening of the second common flow path and flowing liquid recovered from the second common flow path through the second opening to the outflow outlet. Each of the individual flow paths has a pressure chamber in which a pressure applying section is disposed between the one end and the other end and communicates with the discharge hole, a first throttle section that is disposed between the one end and the pressure chamber and has a flow path resistance greater than that of the pressure chamber, and a second throttle section that is disposed between the other end and the pressure chamber and has a flow path resistance greater than that of the pressure chamber. The combined flow path resistance of the second common flow path, the recovery flow path, and the second throttle section is greater than the combined flow path resistance of the first common flow path, the supply flow path, and the first throttle section.

In addition, a liquid ejection head according to one aspect of the present invention comprises a plurality of individual flow paths through which liquid flows, each having one end, another end, and an ejection hole disposed between the one end and the other end for ejecting liquid; a first common flow path having a first opening and connected to the one end of each of the individual flow paths; a second common flow path having a second opening and connected to the other end of each of the individual flow paths; a supply flow path having an inlet through which liquid flows in from the outside and connected to the first opening of the first common flow path and supplying the liquid flowing in from the inlet to the first common flow path through the first opening; and a recovery flow path having an outlet through which liquid flows out to the outside and connected to the second opening of the second common flow path and flowing liquid recovered from the second common flow path through the second opening to the outflow outlet. Each of the individual flow paths has a pressure chamber in which a pressure applying section is disposed between the one end and the other end and communicates with the discharge hole, a first throttle section that is disposed between the one end and the pressure chamber and has a flow resistance greater than that of the pressure chamber, and a second throttle section that is disposed between the other end and the pressure chamber and has a flow resistance greater than that of the pressure chamber. The total cross-sectional area of the second common flow path, the recovery flow path, and the second throttle section is smaller than the total cross-sectional area of the first common flow path, the supply flow path, and the first throttle section.

A liquid ejection device according to another aspect of the present invention includes the above-mentioned liquid ejection head, and a circulation unit that is connected to the inlet and the outlet of the liquid ejection head and circulates liquid through the liquid ejection head.

FIG. 1 is a side view of a printer, which is a liquid ejection apparatus according to an embodiment of the present invention. FIG. 2 is a plan view of the printer. FIG. 3 is a schematic diagram showing the relationship between the liquid ejection head and the circulation unit in the printer. FIG. 4 is a plan view of the first flow path member and the second flow path member included in the head body of the liquid ejection head. FIG. 5 is a cross-sectional view of a main portion of the first flow path member. FIG. 6 is a cross-sectional view of the second flow path member taken along line VI-VI in FIG. FIG. 7 is a cross-sectional view of the second flow path member taken along line VII-VII in FIG. FIG. 8 is a cross-sectional view of the second flow path member taken along line VIII-VIII in FIG. FIG. 9 is a plan view of each plate included in the second flow path member. FIG. 10 is a graph showing a change in flow rate during ejection of ink as a liquid from a liquid ejection head.

Below, a liquid ejection head and a liquid ejection device according to an embodiment of the present invention will be described with reference to the drawings. The liquid ejection device is a device equipped with a liquid ejection head that ejects liquid. Examples of liquid ejection devices include a recording device that ejects ink as a liquid from a liquid ejection head, a device that ejects liquid containing conductive particles from a liquid ejection head to print wiring patterns for electronic devices, and a device that ejects liquid such as a chemical agent from a liquid ejection head toward a reaction vessel to produce a chemical agent. In the following embodiment, an inkjet printer, which is a recording device equipped with a liquid ejection head that ejects ink as a liquid, is given as an example of a specific example of a liquid ejection device. An inkjet printer is a recording device that prints images such as letters and patterns on workpieces such as paper sheets, resin sheets, and fabrics such as woven and knitted fabrics using an inkjet method.

[Printer overall configuration]
1 and 2, the printer 1 includes a liquid ejection head 2 that ejects ink, a movable unit 7 that moves a workpiece W relatively to the liquid ejection head 2, and a control unit 9. In the printer 1, the control unit 9 controls the liquid ejection head 2 based on print data, which is image data, and ejects ink toward the workpiece W moved by the movable unit 7, causing ink droplets to land on the workpiece W, thereby performing recording such as printing on the workpiece W.

In this embodiment, the printer 1 is a so-called line printer in which the liquid ejection head 2 is fixed to a head mounting frame 12 arranged in a head chamber 11. Another embodiment of the printer 1 is a so-called serial printer in which the liquid ejection head 2 is moved back and forth in a direction intersecting the transport direction of the workpiece W, and the operation of ejecting ink from the liquid ejection head 2 and the operation of transporting the workpiece W are alternately performed.

In the printer 1, four flat head mounting frames 12 are arranged in the head chamber 11. Each head mounting frame 12 is equipped with a head group 2A including five liquid ejection heads 2. The printer 1 has four head groups 2A, and is equipped with a total of 20 liquid ejection heads 2.

The liquid ejection head 2 has a long, narrow shape that is elongated in one direction. The liquid ejection head 2 is mounted on the head mounting frame 12 so that the part that ejects ink faces the printing surface of the workpiece W from above and its longitudinal direction is parallel to the direction perpendicular to the transport direction of the workpiece W. In one head group 2A, three liquid ejection heads 2 are lined up along the direction perpendicular to the transport direction of the workpiece W, and the other two liquid ejection heads 2 are lined up one by one between the three liquid ejection heads 2 at positions shifted along the transport direction. In other words, in one head group 2A, the liquid ejection heads 2 are arranged in a staggered manner. In one head group 2A, the liquid ejection heads 2 are arranged so that the range that can be printed by each liquid ejection head 2 is connected in the width direction of the workpiece W, that is, in the direction perpendicular to the transport direction of the workpiece W. By arranging each liquid ejection head 2 in this way in the head group 2A, it is possible to print without gaps in the width direction of the workpiece W based on the ejection of ink from each liquid ejection head 2.

The four head groups 2A are arranged along the transport direction of the workpiece W. Each liquid ejection head 2 belonging to one head group 2A is supplied with the same color ink, and the four head groups 2A can print four colors of ink. The ink colors are, for example, magenta (M), yellow (Y), cyan (C), and black (BK).

The movable part 7 moves the workpiece W relative to the liquid ejection head 2 mounted on the head mounting frame 12 in the head chamber 11. The movable part 7 includes a supply roller 71 and a supply adjustment roller 72 arranged upstream of the head chamber 11 in the transport direction of the workpiece W, a transport roller 73 arranged in the head chamber 11, and a first recovery adjustment roller 74, a second recovery adjustment roller 75, and a recovery roller 76 arranged downstream of the head chamber 11 in the transport direction of the workpiece W. The supply roller 71 is a roller that sends out the workpiece W. The supply adjustment roller 72 is a roller that guides the workpiece W sent out by the supply roller 71 into the head chamber 11. The transport roller 73 is a roller that transports the workpiece W guided by the supply adjustment roller 72 and introduced into the head chamber 11 so that it passes under the liquid ejection head 2. The first recovery adjustment roller 74 and the second recovery adjustment roller 75 are rollers that guide the workpiece W transported by the transport roller 73 to the outside of the head chamber 11. The recovery roller 76 is a roller that recovers the workpiece W that has been guided to the outside of the head chamber 11 by the first recovery adjustment roller 74 and the second recovery adjustment roller 75 by winding it up.

As shown in Figures 1 and 2, the printer 1 according to this embodiment includes an application section 81 arranged between the supply adjustment roller 72 and the head chamber 11 in the transport direction of the workpiece W, a drying section 82 arranged between the first collection adjustment roller 74 and the second collection adjustment roller 75, and an imaging section 83 arranged between the second collection adjustment roller 75 and the collection roller 76.

The application section 81 applies a coating agent to the workpiece W before it is introduced into the head chamber 11. For example, when the workpiece W is made of a material into which ink does not easily penetrate, a coating agent that forms an ink-receiving layer on the workpiece W so that the ink can easily adhere can be used. In addition, when the workpiece W is made of a material into which ink easily penetrates, a coating agent that forms an ink-penetration suppressing layer on the workpiece W can be used so that the ink does not bleed too much and does not mix too much with other inks that land next to it.

The drying section 82 dries the ink adhering to the workpiece W before it is collected by the collection roller 76. Examples of ink drying methods used by the drying section 82 include blowing hot air, irradiating infrared rays, and contacting the workpiece with a heated roller.

The imaging unit 83 captures an image of the workpiece W after drying by the drying unit 82, and acquires imaging data for checking the printing state of the ink on the workpiece W. The imaging data acquired by the imaging unit 83 is input to the control unit 9. The control unit 9 evaluates the printing state of the ink on the workpiece W based on the imaging data. Specifically, the control unit 9 evaluates whether there are any pixels that are not printed because ink droplets were not ejected from the liquid ejection head 2, whether the landing positions of the ink droplets ejected from the liquid ejection head 2 are shifted, etc.

[Detailed configuration of liquid ejection head]
Next, the liquid ejection head 2 will be described in detail with reference to Figures 3 to 9. In the following description, the outside of the liquid ejection head 2 will be referred to as the "exterior." The liquid ejection head 2 includes a head body 21 in which ink flow paths for ejecting ink are formed, and a housing 22 that is connected to the head body 21 and contains a driver IC, a wiring board, and the like for controlling the ink ejection operation.

The head body 21 has a flat plate shape that is long in one direction. In the following, regarding the directional relationship, one direction in the longitudinal direction D1 of the head body 21 is referred to as the first direction D11, and the opposite direction of the first direction D11 is referred to as the second direction D12. In addition, one direction in the width direction D2 perpendicular to the longitudinal direction D1 of the head body 21 is referred to as the third direction D21, and the opposite direction of the third direction D21 is referred to as the fourth direction D22. In addition, the direction perpendicular to the longitudinal direction D1 and the width direction D2 of the head body 21 is referred to as the thickness direction D3 of the head body 21. When the liquid ejection head 2 is mounted on the head mounting frame 12, the longitudinal direction D1 of the head body 21 is parallel to the direction perpendicular to the transport direction of the workpiece W, the width direction D2 of the head body 21 is parallel to the transport direction of the workpiece W, and the thickness direction D3 of the head body 21 is parallel to the up-down direction perpendicular to the printing surface of the workpiece W.

3, the head body 21 includes a first flow path member 3 arranged in a lower portion of the head body 21, a second flow path member 4 arranged in an upper portion of the head body 21, and a piezoelectric actuator substrate 5 arranged between the first flow path member 3 and the second flow path member 4. The first flow path member 3 is a flat member in which a flow path for ejecting ink in response to driving of the piezoelectric actuator substrate 5 is formed. The second flow path member 4 is a flat member having an inlet 411 through which ink flows in from the outside, and an outlet 421 through which ink flows out to the outside. The second flow path member 4 is formed with a flow path for supplying the ink flowing in from the inlet 411 to the first flow path member 3, and a flow path for flowing the ink recovered from the first flow path member 3 to the outlet 421.

As shown in FIG. 3, a circulation unit 6 is disposed outside the liquid ejection head 2. The circulation unit 6 is connected to the inlet 411 and the outlet 421 in the head body 21. The circulation unit 6 circulates the ink through the head body 21 by forming a flow of ink from the outlet 421 to the inlet 411.

The circulation section 6 includes a supply storage section 61, a recovery storage section 62, a pump 63, an external supply flow path member 64, and an external recovery flow path member 65. The supply storage section 61 stores ink supplied to the inlet 411 of the head body 21. The recovery storage section 62 stores ink flowing out from the outlet 421 of the head body 21. The pump 63 sends ink from the recovery storage section 62 to the supply storage section 61. The external supply flow path member 64 connects the supply storage section 61 and the inlet 411 of the head body 21, forming a flow path that flows the ink stored in the supply storage section 61 to the inlet 411. The external recovery flow path member 65 connects the recovery storage section 62 and the outlet 421 of the head body 21, forming a flow path that flows the ink flowing out from the outlet 421 to the recovery storage section 62.

As shown in FIG. 4 and FIG. 5, the first flow path member 3 arranged in the lower part of the head main body 21 has a plurality of individual flow paths 31, a first common flow path 32, and a second common flow path 33. The first common flow path 32 is a flow path connected to one end 311 which is an inlet of each of the plurality of individual flow paths 31. The second common flow path 33 is a flow path connected to the other end 312 which is an outlet of each of the plurality of individual flow paths 31. In this embodiment, the first flow path member 3 has a plurality of first common flow paths 32 connected to one end 311 of each of the plurality of individual flow paths 31, and has a plurality of second common flow paths 33 connected to the other end 312 of each of the plurality of individual flow paths 31. For example, the first flow path member 3 has four first common flow paths 32 and four second common flow paths 33.

Each of the individual flow paths 31 has one end 311 connected to the first common flow path 32 and the other end 312 connected to the second common flow path 33, and is a flow path through which ink flows from the one end 311 to the other end 312. In each individual flow path 31, the one end 311 is the upstream end in the ink flow direction and is the inlet of the flow path, and the other end 312 is the downstream end in the ink flow direction and is the outlet of the flow path. The shape of the flow path cross section perpendicular to the ink flow direction in each individual flow path 31 is, for example, rectangular. Each individual flow path 31 has a pressure chamber 313 arranged on the upper surface 3A of the first flow path member 3 between the one end 311 and the other end 312, an ejection hole 315 arranged on the lower surface 3B of the first flow path member 3 between the one end 311 and the other end 312, and a descender 314 connecting the pressure chamber 313 and the ejection hole 315.

The pressure chamber 313 opens upward on the upper surface 3A of the first flow path member 3 and is connected to the discharge hole 315 through the descender 314. A piezoelectric actuator substrate 5 is bonded to the upper surface 3A of the first flow path member 3 so as to close the opening of the pressure chamber 313. As a result, a displacement element 51 incorporated in the piezoelectric actuator substrate 5 is disposed above the pressure chamber 313. The displacement element 51 functions as a pressure applying section that applies pressure to the pressure chamber 313. The descender 314 extends downward from the pressure chamber 313 to the discharge hole 315 along the thickness direction D3 of the first flow path member 3. The pressure chamber 313 is connected to the upper end of the descender 314, and the discharge hole 315 is connected to the lower end of the descender 314. The discharge hole 315 opens downward on the lower surface 3B of the first flow path member 3 and discharges ink that has been pressurized in the pressure chamber 313 and passed through the descender 314 in response to the drive of the displacement element 51.

Each of the multiple first common flow paths 32 is a flow path extending along the longitudinal direction D1 of the first flow path member 3. The flow direction of ink in each first common flow path 32 is parallel to the longitudinal direction D1 of the first flow path member 3. Each first common flow path 32 is connected to one end 311 of each of the multiple individual flow paths 31, thereby functioning as a flow path of a supply system that supplies ink to each individual flow path 31. The shape of the flow path cross section perpendicular to the ink flow direction in each first common flow path 32 is, for example, rectangular. The flow path cross-sectional area indicating the area of the flow path cross section in each first common flow path 32 is the same throughout between both ends in the longitudinal direction D1. In other words, the flow path cross-sectional area of each first common flow path 32 is uniform in the ink flow direction. Each first common flow path 32 is arranged side by side in the width direction D2 of the first flow path member 3. Each first common flow path 32 has a first opening 321 at each end in the first direction D11 and the second direction D12 in the longitudinal direction D1, which receives ink supplied from the second flow path member 4 to the first flow path member 3. In each first common flow path 32, approximately the same amount of ink is supplied from the second flow path member 4 to the first opening 321 formed at the end in the first direction D11 and the first opening 321 formed at the end in the second direction D12. The ink supplied to the first opening 321 at each end of the first common flow path 32 flows toward the center of the first common flow path 32 in the longitudinal direction D1. The ink flowing through the first common flow path 32 is supplied to each individual flow path 31 whose one end 311 is connected to the first common flow path 32.

A first filter 311A is provided at the connection between the first common flow path 32 and one end 311 of each individual flow path 31. The first filter 311A allows the ink in the first common flow path 32 to pass to each individual flow path 31, while restricting foreign matter in the ink from passing to each individual flow path 31.

In the first flow path member 3, the lower surface of the first common flow path 32 is the first damper 322. The surface of the first damper 322 opposite to the surface facing the first common flow path 32 faces the first damper chamber 323 containing a gas such as air. The volume of the first damper chamber 323 changes depending on the pressure applied from the first common flow path 32. The first damper 322 can vibrate in response to the change in the volume of the first damper chamber 323. By damping the vibration of the first damper 322, it is possible to damp the pressure fluctuation occurring in the first common flow path 32. Therefore, by providing the first damper 322 for the first common flow path 32, it is possible to reduce pressure fluctuations such as resonance of the ink in the first common flow path 32.

Each of the second common flow paths 33 is a flow path extending along the longitudinal direction D1 at a position below the first common flow path 32 in the first flow path member 3. The flow direction of the ink in each second common flow path 33 is parallel to the longitudinal direction D1 of the first flow path member 3. Each second common flow path 33 is connected to the other end 312 of each of the multiple individual flow paths 31, and functions as a flow path of a recovery system that recovers ink that has not been ejected from the ejection hole 315 in each individual flow path 31. The shape of the flow path cross section perpendicular to the ink flow direction in each second common flow path 33 is, for example, rectangular. The flow path cross-sectional area indicating the area of the flow path cross section in each second common flow path 33 is the same throughout the entire area between both ends in the longitudinal direction D1. In other words, the flow path cross-sectional area of each second common flow path 33 is uniform in the ink flow direction. Each second common flow path 33 is arranged side by side in the width direction D2 of the first flow path member 3. Each second common flow path 33 has a second opening 331 at each end in the first direction D11 and at each end in the second direction D12 in the longitudinal direction D1, which allows ink that is not ejected from the ejection hole 315 in each individual flow path 31 and is collected in the second common flow path 33 to flow to the second flow path member 4. The ink collected in the second common flow path 33 from each individual flow path 31 whose other end 312 is connected to the second common flow path 33 flows toward the second opening 331 at each end of the second common flow path 33 and is collected in the second flow path member 4 through the second opening 331.

In the first flow path member 3, the lower surface of the second common flow path 33 is the second damper 332. The surface of the second damper 332 opposite to the surface facing the second common flow path 33 faces a second damper chamber 333 containing a gas such as air. The volume of the second damper chamber 333 changes depending on the pressure applied from the second common flow path 33. The second damper 332 can vibrate in response to the change in the volume of the second damper chamber 333. By damping the vibration of the second damper 332, it is possible to damp the pressure fluctuation occurring in the second common flow path 33. Therefore, by providing the second damper 332 for the second common flow path 33, it is possible to reduce pressure fluctuations such as resonance of the ink in the second common flow path 33.

The first common flow path 32 and the second common flow path 33 are arranged to overlap each other in a plan view in the thickness direction D3 of the first flow path member 3. The multiple individual flow paths 31 are arranged side by side in the longitudinal direction D1 on both sides of the first common flow path 32 and the second common flow path 33 in the width direction D2, with one end 311 connected to the first common flow path 32 and the other end 312 connected to the second common flow path 33.

Each of the multiple individual flow paths 31 has a first throttling section 316 disposed between one end 311 and the pressurized chamber 313, and a second throttling section 317 connected to the lower end of a descender 314 having a discharge hole 315 between the other end 312 and the pressurized chamber 313.

The first throttling section 316 is a flow path extending along the width direction D2 of the first flow path member 3 between one end 311 of the individual flow path 31 and the pressure chamber 313. The first throttling section 316 is connected to each of the first common flow path 32 connected to one end 311 of the individual flow path 31 and the pressure chamber 313. The ink flow direction in the first throttling section 316 is parallel to the width direction D2 of the first flow path member 3. The shape of the flow path cross section perpendicular to the ink flow direction in the first throttling section 316 is, for example, rectangular. The flow path cross-sectional area indicating the area of the flow path cross section in the first throttling section 316 is the same throughout between both end portions. In other words, the flow path cross-sectional area of the first throttling section 316 is uniform in the ink flow direction. The flow path cross-sectional area of the first throttling section 316 is smaller than the flow path cross-sectional area of the first common flow path 32, and is smaller than each of the flow path cross-sectional areas of the pressure chamber 313 and the descender 314. As a result, the flow resistance of the first throttle section 316 is greater than the flow resistance of the first common flow path 32, and is greater than the flow resistance of each of the pressure chamber 313 and the descender 314.

The second throttling section 317 is a flow path extending along the width direction D2 of the first flow path member 3 between the other end 312 of the individual flow path 31 and the lower end of the descender 314. The second throttling section 317 is connected to the second common flow path 33 connected to the other end 312 of the individual flow path 31, and is also connected to the pressure chamber 313 and the ejection hole 315 through the descender 314. The ink flow direction in the second throttling section 317 is parallel to the width direction D2 of the first flow path member 3. The shape of the flow path cross section perpendicular to the ink flow direction in the second throttling section 317 is, for example, rectangular. The flow path cross-sectional area indicating the area of the flow path cross section in the second throttling section 317 is the same throughout between both ends. In other words, the flow path cross-sectional area of the second throttling section 317 is uniform in the ink flow direction. The flow path cross-sectional area of the second throttle section 317 is smaller than the flow path cross-sectional area of the second common flow path 33, and is also smaller than the flow path cross-sectional area of each of the pressurizing chamber 313 and the descender 314. As a result, the flow path resistance of the second throttle section 317 is larger than the flow path resistance of the second common flow path 33, and is also larger than the flow path resistance of each of the pressurizing chamber 313 and the descender 314.

In the first flow path member 3 in which the individual flow paths 31, the first common flow path 32, and the second common flow path 33 are formed, the ink supplied from the second flow path member 4 to the first flow path member 3 flows into the first common flow path 32 through the first opening 321. The ink that flows into the first common flow path 32 flows into each individual flow path 31 through one end 311, which is the connection part with the first common flow path 32. The ink that flows into each individual flow path 31 through the one end 311 flows into the pressure chamber 313 after passing through the first throttling section 316. The ink that flows into the pressure chamber 313 flows through the descender 314, and some of the ink is ejected from the ejection hole 315. The ink that is not ejected from the ejection hole 315 flows into the second common flow path 33 through the other end 312 after passing through the second throttling section 317. The ink that flows into the second common flow path 33 flows toward the second flow path member 4 through the second opening 331 and is collected.

As shown in FIG. 5, the first flow path member 3 has a layered structure in which multiple plates are stacked in the thickness direction D3. In the example of FIG. 5, the first flow path member 3 has 16 plates, the 1st to 16th plates 3a to 3p, stacked in order from the top.

One end 311 of each individual flow path 31 is defined by a hole formed in the fourth plate 3d, and the other end 312 of each individual flow path 31 is defined by a hole formed in the eleventh plate 3k. The pressure chamber 313 in each individual flow path 31 is defined by a hole formed in the first plate 3a of the top layer. The descender 314 in each individual flow path 31 is defined by a hole formed in each of the second to fifteenth plates 3b to 3o so as to communicate with the hole in the first plate 3a that defines the pressure chamber 313. The discharge hole 315 in each individual flow path 31 is defined by a hole formed in the sixteenth plate 3p of the bottom layer so as to communicate with the hole in the second to fifteenth plates 3b to 3o that defines the descender 314. The first throttle section 316 in each individual flow path 31 is defined by a hole formed in the third plate 3c so as to communicate with the hole in the fourth plate 3d that defines the one end 311 and the hole in the first plate 3a that defines the pressurizing chamber 313. The second throttle section 317 in each individual flow path 31 is defined by a hole formed in the fifteenth plate 3o so as to communicate with the hole in the eleventh plate 3k that defines the other end 312, the hole in the fifteenth plate 3o that defines the lower end of the descender 314, and the hole in the sixteenth plate 3p that defines the discharge hole 315.

Each first common flow path 32 is defined by a hole formed in each of the fifth to eighth plates 3e to 3h so as to communicate with the hole in the fourth plate 3d that defines one end 311 of each individual flow path 31. The first damper 322 corresponding to each first common flow path 32 is formed by the ninth plate 3i that faces the hole in the eighth plate 3h that defines the lower end of the first common flow path 32, and the first damper chamber 323 corresponding to the first damper 322 is defined by a groove formed in the tenth plate 3j.

Each second common flow path 33 is defined by a hole formed in each of the 11th to 12th plates 3k to 3l so as to communicate with the hole in the 11th plate 3k that defines the other end 312 of each individual flow path 31. The second damper 332 corresponding to each second common flow path 33 is formed by the 13th plate 3m facing the hole in the 12th plate 3l that defines the lower end of the second common flow path 33, and the second damper chamber 333 corresponding to the second damper 332 is defined by a groove formed in the 14th plate 3n.

The second flow path member 4, which is disposed in the upper portion of the head body 21, is joined to an area of the upper surface 3A of the first flow path member 3 where the piezoelectric actuator substrate 5 is not connected. In other words, the second flow path member 4 is joined to the upper surface 3A of the first flow path member 3 so as to surround the piezoelectric actuator substrate 5. As shown in Figures 4 and 6 to 9, the second flow path member 4 has a supply flow path 41 and a recovery flow path 42.

The supply flow path 41 is a flow path through which ink flows to be supplied to each first common flow path 32 in the first flow path member 3. The supply flow path 41 has an inlet 411 into which ink flows through the external supply flow path member 64 of the circulation unit 6 connected to the head body 21 outside the liquid ejection head 2. The inlet 411 faces upward and opens to the outside in the end region in the second direction D12 in the longitudinal direction D1 of the second flow path member 4. The supply flow path 41 is connected to the first opening 321 of each first common flow path 32, and supplies the ink that flows in from the inlet 411 to each first common flow path 32 through the first opening 321.

The supply flow path 41 has an inflow connection flow path 412A connected to the inlet 411, a supply storage chamber 412 that communicates with the inlet 411 through the inflow connection flow path 412A, a branch connection flow path 4131 that is connected to the supply storage chamber 412, and a supply branch flow path 413 that communicates with the supply storage chamber 412 through the branch connection flow path 4131.

The inflow connection flow path 412A is a flow path that connects the inlet 411 and the supply storage chamber 412. The supply storage chamber 412 is a flow path that is arranged in a region on the second direction D12 side from the center of the second flow path member 4 in the longitudinal direction D1, and extends along the longitudinal direction D1 of the second flow path member 4. The ink flow direction in the supply storage chamber 412 is parallel to the longitudinal direction D1 of the second flow path member 4. The shape of the flow path cross section perpendicular to the ink flow direction in the supply storage chamber 412 is, for example, rectangular. The flow path cross-sectional area indicating the area of the flow path cross section in the supply storage chamber 412 is the same throughout between both ends in the longitudinal direction D1. In other words, the flow path cross-sectional area of the supply storage chamber 412 is uniform in the ink flow direction. The supply storage chamber 412 is capable of storing ink that has flowed in from the inlet 411, and has a supply external opening 412B that faces upward and opens to the outside.

The supply external opening 412B of the supply storage chamber 412 is blocked by an elastic film 43 that can be elastically deformed. The volume of the supply storage chamber 412 changes according to the elastic deformation of the portion of the elastic film 43 that faces the supply external opening 412B. The elastic film 43 can vibrate according to the elastic deformation that changes the volume of the supply storage chamber 412. By damping the vibration of the elastic film 43, it is possible to dampen the pressure fluctuations that occur in the supply storage chamber 412. Therefore, by blocking the supply external opening 412B of the supply storage chamber 412 with the elastic film 43, it is possible to reduce pressure fluctuations such as those caused by resonance of the ink in the supply storage chamber 412.

A second filter 412C is also provided in the supply chamber 412. The second filter 412C allows the ink in the supply chamber 412 to pass through to the supply branch flow path 413, while preventing foreign matter in the ink from passing through to the supply branch flow path 413.

The branch connection flow path 4131 is disposed in the center of the second flow path member 4 in the longitudinal direction D1, and is a flow path that connects the supply storage chamber 412 and the supply branch flow path 413.

The supply branch flow path 413 is a flow path that communicates with the supply storage chamber 412 through the branch connection flow path 4131, and is also connected to the first opening 321 in the first flow path member 3, thereby communicating with the first common flow path 32. The supply branch flow path 413 has a first supply branch flow path 413A and a second supply branch flow path 413B.

The first supply branch flow path 413A is connected to the branch connection flow path 4131 at the center of the longitudinal direction D1 of the second flow path member 4 and extends along the longitudinal direction D1. The first supply branch flow path 413A branches from the portion connected to the branch connection flow path 4131 and includes a flow path extending toward the first direction D11 and a flow path extending toward the second direction D12. The ink flow direction in the first supply branch flow path 413A is parallel to the longitudinal direction D1 of the second flow path member 4. The shape of the flow path cross section perpendicular to the ink flow direction in the first supply branch flow path 413A is, for example, rectangular. The flow path cross-sectional area indicating the area of the flow path cross section in the first supply branch flow path 413A is the same throughout the entire area between both ends in the longitudinal direction D1. In other words, the flow path cross-sectional area of the first supply branch flow path 413A is uniform in the ink flow direction.

The second supply branch flow path 413B is a flow path that is connected to the end of the first supply branch flow path 413A in the first direction D11 and the end of the second direction D12 in the longitudinal direction D1, respectively, and extends in the width direction D2, and is connected to the first opening 321 of each first common flow path 32 in the first flow path member 3. The second supply branch flow path 413B includes a flow path that branches off from a portion connected to the first supply branch flow path 413A and extends toward the third direction D21 in the width direction D2, and a flow path that extends toward the fourth direction D22 in the width direction D2. The ink flow direction in the second supply branch flow path 413B is parallel to the width direction D2 of the second flow path member 4. The shape of the flow path cross section perpendicular to the ink flow direction in the second supply branch flow path 413B is, for example, rectangular. The flow path cross-sectional area indicating the area of the flow path cross section in the second supply branch flow path 413B is the same throughout between both ends. That is, the cross-sectional area of the second supply branch flow path 413B is uniform in the ink flow direction.

The recovery flow path 42 is a flow path through which ink recovered from each second common flow path 33 in the first flow path member 3 flows. The recovery flow path 42 has an outlet 421 through which ink flows out to the external recovery flow path member 65 of the circulation unit 6 connected to the head body 21 outside the liquid ejection head 2. The outlet 421 faces upward and opens to the outside in the end region in the first direction D11 in the longitudinal direction D1 of the second flow path member 4. The recovery flow path 42 is connected to the second opening 331 of each second common flow path 33, and causes the ink recovered from each second common flow path 33 to flow through the second opening 331 to the outlet 421.

The recovery flow path 42 has an outflow connection flow path 422A connected to the outflow outlet 421, a recovery storage chamber 422 that communicates with the outflow outlet 421 through the outflow connection flow path 422A, and a recovery branch flow path 423 that communicates with the recovery storage chamber 422.

The outflow connection flow path 422A is a flow path that connects the outflow port 421 and the recovery storage chamber 422. The recovery storage chamber 422 is a flow path that is arranged in a region on the first direction D11 side from the center of the second flow path member 4 in the longitudinal direction D1, and extends along the longitudinal direction D1 of the second flow path member 4. The ink flow direction in the recovery storage chamber 422 is parallel to the longitudinal direction D1 of the second flow path member 4. The shape of the flow path cross section perpendicular to the ink flow direction in the recovery storage chamber 422 is, for example, rectangular. The flow path cross-sectional area indicating the area of the flow path cross section in the recovery storage chamber 422 is the same throughout between both ends in the longitudinal direction D1. In other words, the flow path cross-sectional area of the recovery storage chamber 422 is uniform in the ink flow direction. The recovery storage chamber 422 is capable of storing ink flowing out from the outflow port 421, and has a recovery external opening 422B that faces upward and opens to the outside.

The recovery storage chamber 422 is disposed adjacent to the supply storage chamber 412 in the longitudinal direction D1 of the second flow path member 4. The recovery external opening 422B of the recovery storage chamber 422 is blocked by the same elastic film 43 as the supply external opening 412B of the supply storage chamber 412. The volume of the recovery storage chamber 422 changes according to the elastic deformation of the portion of the elastic film 43 facing the recovery external opening 422B. The elastic film 43 can vibrate according to the elastic deformation that changes the volume of the recovery storage chamber 422. The vibration of the elastic film 43 is damped, thereby damping the pressure fluctuations that occur in the recovery storage chamber 422. Therefore, by blocking the recovery external opening 422B of the recovery storage chamber 422 with the elastic film 43, pressure fluctuations such as resonance of the ink in the recovery storage chamber 422 can be reduced.

The supply external opening 412B of the supply storage chamber 412 and the recovery external opening 422B of the recovery storage chamber 422 may be blocked by separate independent elastic films. That is, the supply external opening 412B of the supply storage chamber 412 may be blocked by a first elastic film, while the recovery external opening 422B of the recovery storage chamber 422 may be blocked by a second elastic film. When the supply external opening 412B of the supply storage chamber 412 and the recovery external opening 422B of the recovery storage chamber 422 are blocked by a common elastic film 43, the elastic film 43 is a film formed integrally with the first elastic film blocking the supply external opening 412B and the second elastic film blocking the recovery external opening 422B.

The recovery branch flow path 423 is a flow path that communicates with the recovery storage chamber 422 and is connected to the second opening 331 in the first flow path member 3, thereby communicating with the second common flow path 33. The recovery branch flow path 423 has a first recovery branch flow path 423A and a second recovery branch flow path 423B.

The first recovery branch flow path 423A is a flow path that is connected to the recovery storage chamber 422 at the center of the longitudinal direction D1 of the second flow path member 4 and extends along the longitudinal direction D1. The first recovery branch flow path 423A includes a flow path that branches from a portion connected to the recovery storage chamber 422 and extends toward the first direction D11 and a flow path that extends toward the second direction D12. The first recovery branch flow path 423A is disposed at a position above the first supply branch flow path 413A in the second flow path member 4. In a plan view seen in the thickness direction D3 of the second flow path member 4, the first supply branch flow path 413A and the first recovery branch flow path 423A are disposed so that at least a portion of them overlap each other. The ink flow direction in the first recovery branch flow path 423A is parallel to the longitudinal direction D1 of the second flow path member 4. The shape of the flow path cross section perpendicular to the ink flow direction in the first recovery branch flow path 423A is, for example, rectangular. The flow path cross-sectional area, which indicates the area of the flow path cross section in the first recovery branch flow path 423A, is the same throughout between both ends in the longitudinal direction D1. In other words, the flow path cross-sectional area of the first recovery branch flow path 423A is uniform in the ink flow direction.

The second recovery branch flow path 423B is a flow path that is connected to the end of the first recovery branch flow path 423A in the first direction D11 and the end of the second direction D12 in the longitudinal direction D1, respectively, and extends in the width direction D2, and is connected to the second opening 331 of each second common flow path 33 in the first flow path member 3. The second recovery branch flow path 423B includes a flow path that branches off from a portion connected to the first recovery branch flow path 423A and extends toward the third direction D21 in the width direction D2, and a flow path that extends toward the fourth direction D22 in the width direction D2. The ink flow direction in the second recovery branch flow path 423B is parallel to the width direction D2 of the second flow path member 4. The shape of the flow path cross section perpendicular to the ink flow direction in the second recovery branch flow path 423B is, for example, rectangular. The flow path cross-sectional area indicating the area of the flow path cross section in the second recovery branch flow path 423B is the same throughout between both ends. That is, the cross-sectional area of the second recovery branch channel 423B is uniform in the ink flow direction.

In the second flow path member 4 in which the supply flow path 41 and the recovery flow path 42 are formed, ink stored in the supply storage section 61 of the circulation section 6 connected to the head body 21 is supplied to the second flow path member 4 through the external supply flow path member 64. The ink supplied to the second flow path member 4 through the external supply flow path member 64 flows into the supply storage chamber 412 through the inlet 411 and the inlet connection flow path 412A. The ink that flows into the supply storage chamber 412 flows into the first supply branch flow path 413A through the branch connection flow path 4131. The ink that flows into the first supply branch flow path 413A flows into the second supply branch flow path 413B after flowing through the first supply branch flow path 413A. The ink that flows into the second supply branch flow path 413B is supplied to each first common flow path 32 of the first flow path member 3 through the first opening 321 connected to the second supply branch flow path 413B. On the other hand, in the second flow path member 4, the ink recovered from each second common flow path 33 flows into the second recovery branch flow path 423B connected to the second opening 331 of each second common flow path 33 in the first flow path member 3. The ink that flows into the second recovery branch flow path 423B flows into the first recovery branch flow path 423A, and after flowing through the first recovery branch flow path 423A, flows into the recovery storage chamber 422. The ink that flows into the recovery storage chamber 422 flows out from the outlet 421 through the outflow connection flow path 422A. The ink that flows out from the outlet 421 flows into the recovery storage section 62 through the external recovery flow path member 65 connected to the outlet 421. The ink that flows into the recovery storage section 62 and is stored therein is sent from the recovery storage section 62 to the supply storage section 61 by the pump 63. As a result, the ink circulates through the head main body 21 including the first flow path member 3 and the second flow path member 4.

Also, as shown in FIG. 6, the lower surface of the second flow path member 4 is provided with a storage space 44 for the piezoelectric actuator substrate 5. The storage space 44 has through holes 441 that penetrate to the upper surface of the second flow path member 4 at each end in the third direction D21 and the fourth direction D22 in the width direction D2 of the second flow path member 4. A signal transmission part 442 such as an FPC (Flexible Printed Circuit) that transmits a drive signal to drive the piezoelectric actuator substrate 5 passes through the through holes 441.

As shown in Figures 6 to 9, the second flow path member 4 has a layered structure in which multiple plates are stacked in the thickness direction D3. In the example of Figure 6, the second flow path member 4 has seven plates, the first to seventh plates 4a to 4g, stacked in order from the top.

The inlet 411 in the supply flow passage 41 and the outlet 421 in the recovery flow passage 42 are defined by holes formed in the first and

second plates

4a and 4b. The supply storage chamber 412 in the supply flow passage 41 and the recovery storage chamber 422 in the recovery flow passage 42 are defined by holes formed in the second and

third plates

4b and 4c. The elastic film 43, which commonly blocks the supply external opening 412B of the supply storage chamber 412 and the recovery external opening 422B of the recovery storage chamber 422, is sandwiched and disposed between the first plate 4a and the second plate 4b. The inflow connection flow passage 412A in the supply flow passage 41 and the outflow connection flow passage 422A in the recovery flow passage 42 are defined by holes formed in the third plate 4c. The branch connection flow passage 4131 in the supply flow passage 41 is defined by a hole formed in the fourth plate 4d. The first supply branch flow passage 413A in the supply flow passage 41 is defined by a hole formed in the fifth plate 4e. The first recovery branch flow path 423A in the recovery flow path 42 is defined by a groove formed in the third plate 4c. The second supply branch flow path 413B in the supply flow path 41 is defined by holes formed in the fifth and

sixth plates

4e and 4f. The second recovery branch flow path 423B in the recovery flow path 42 is defined by holes formed in the fourth to sixth plates 4d to 4f.

The storage space 44 that houses the piezoelectric actuator substrate 5 is defined by a hole formed in the seventh plate 4g. The through hole 441 through which the signal transmission part 442 passes is defined by holes formed in the first to seventh plates 4a to 4g.

The piezoelectric actuator substrate 5 accommodated in the accommodation space 44 on the lower surface of the second flow path member 4 is bonded to the upper surface 3A of the first flow path member 3. The piezoelectric actuator substrate 5 is arranged so that the displacement elements 51 are located above each of the pressure chambers 313 of each individual flow path 31. The openings of each of the pressure chambers 313 of each individual flow path 31 are blocked by bonding the piezoelectric actuator substrate 5 to the upper surface 3A of the first flow path member 3. A signal transmission unit 442 such as an FPC for supplying a signal to the displacement elements 51 is connected to the piezoelectric actuator substrate 5.

5, the piezoelectric actuator substrate 5 has a laminated structure made up of two piezoelectric layers, a first piezoelectric ceramic layer 5A and a second piezoelectric ceramic layer 5B. Both the first piezoelectric ceramic layer 5A and the second piezoelectric ceramic layer 5B extend so as to straddle the multiple pressure chambers 313. The first piezoelectric ceramic layer 5A and the second piezoelectric ceramic layer 5B are made of a ceramic material having ferroelectricity, such as lead zirconate titanate (PZT)-based, _NaNbO3- based, BaTiO3 _- based, (BiNa) _NbO3- based, or _BiNaNb5O15 _- based.

The piezoelectric actuator substrate 5 has a common electrode 52 made of a metal material such as Ag-Pd, and individual electrodes 53 made of a metal material such as Au. The individual electrodes 53 are arranged at positions facing each pressure chamber 313 on the upper surface of the piezoelectric actuator substrate 5. A drive signal is supplied to the individual electrodes 53 from the control unit 9 through the signal transmission unit 442. The drive signal is supplied at a constant period in synchronization with the transport of the workpiece W. The common electrode 52 is formed over almost the entire surface in the surface direction in the region between the first piezoelectric ceramic layer 5A and the second piezoelectric ceramic layer 5B. In other words, the common electrode 52 extends so as to cover all the pressure chambers 313 in the region facing the piezoelectric actuator substrate 5. The common electrode 52 is connected to a surface electrode for a common electrode (not shown) formed on the first piezoelectric ceramic layer 5A at a position avoiding the electrode group consisting of the individual electrodes 53, via a through conductor formed through the first piezoelectric ceramic layer 5A. The common electrode 52 is also grounded via the surface electrode for a common electrode and is held at ground potential. The surface electrode for the common electrode is connected directly or indirectly to the control unit 9, similar to the individual electrodes 53.

The portion of the first piezoelectric ceramic layer 5A sandwiched between the individual electrode 53 and the common electrode 52 is polarized in the thickness direction D3, forming a displacement element 51 with a unimorph structure. The displacement element 51 is driven (displaced) by a drive signal supplied to the individual electrode 53 via a driver IC or the like under the control of the control unit 9. Ink can be ejected from the ejection hole 315 by various drive signals. For example, ink can be ejected from the ejection hole 315 by supplying a pulse drive signal to the individual electrode 53 that has a low potential for a certain period of time based on a high potential.

Specifically, the individual electrode 53 is set to a higher potential (high potential) than the common electrode 52 in advance, and each time an ejection request is made, the individual electrode 53 is temporarily set to the same potential (low potential) as the common electrode 52, and then set to a high potential again at a predetermined timing. As a result, when the individual electrode 53 becomes low potential, the first piezoelectric ceramic layer 5A and the second piezoelectric ceramic layer 5B begin to return to their original flat shape, and the volume of the pressure chamber 313 increases compared to the initial state. As a result, negative pressure is applied to the ink in the pressure chamber 313. Then, the ink in the pressure chamber 313 begins to vibrate with a natural vibration period. Specifically, first, the volume of the pressure chamber 313 begins to increase, and the negative pressure gradually decreases. Next, the volume of the pressure chamber 313 becomes maximum, and the pressure becomes almost zero. Next, the volume of the pressure chamber 313 begins to decrease, and the pressure increases. After that, when the pressure becomes almost maximum, the individual electrode 53 is set to a high potential. Then, the vibration applied first and the vibration applied next overlap, and a larger pressure is applied to the ink. This pressure propagates through the descender 314, causing ink to be ejected from the ejection hole 315.

In other words, ink can be ejected from the ejection hole 315 by supplying a pulse drive signal to the individual electrode 53 that has a low potential for a certain period of time, with a high potential as the reference. If the pulse width is set to AL (Acoustic Length), which is half the natural vibration period of the ink in the pressure chamber 313, then in principle, the ink ejection speed and ejection volume can be maximized.

In the liquid ejection head 2 according to this embodiment, in each individual flow path 31, the first throttling section 316 is a flow path connecting the first common flow path 32 and the pressure chamber 313, and the second throttling section 317 is a flow path connecting the second common flow path 33 and the pressure chamber 313. Therefore, in order to ensure appropriate ejection characteristics of ink from the ejection holes 315 in each individual flow path 31, it is required that the flow path resistance of the first throttling section 316 is set with high precision to a value greater than the flow path resistance of each of the first common flow path 32, the pressure chamber 313, and the descender 314. Similarly, it is required that the flow path resistance of the second throttling section 317 is set with high precision to a value greater than the flow path resistance of each of the second common flow path 33, the pressure chamber 313, and the descender 314.

If the flow resistance of the first throttling section 316 and the second throttling section 317 is too small, the pressure wave generated in the pressure chamber 313 of one individual flow path 31 may be transmitted to the other individual flow paths 31 via the first common flow path 32 and the second common flow path 33, causing crosstalk in which the amount of ink ejected from the ejection hole 315 of each individual flow path 31 becomes unstable. If crosstalk occurs in this way, it becomes difficult to ensure appropriate ejection characteristics of ink from the ejection hole 315 in each individual flow path 31. On the other hand, if the flow resistance of the first throttling section 316 and the second throttling section 317 is too large, the amount of ink supplied from the first common flow path 32 to each individual flow path 31 decreases, and the amount of ink recovered from each individual flow path 31 to the second common flow path 33 decreases. In this case, it also becomes difficult to ensure appropriate ejection characteristics of ink from the ejection hole 315 in each individual flow path 31. In order to ensure appropriate ink ejection characteristics from the ejection holes 315 in each individual flow path 31, it is necessary to set the flow path resistance of each of the first throttle section 316 and the second throttle section 317 to a relatively large value with high precision.

In the liquid ejection head 2 according to this embodiment, the flow path resistance of each of the first and

second throttling sections

316 and 317 in each individual flow path 31 is set so that the difference between the flow path resistances falls within a predetermined tolerance range. This allows the flow path resistance of each of the first and

second throttling sections

316 and 317 to be set to a relatively large value with high precision, compared to a case where the difference in the flow path resistance between the first and

second throttling sections

316 and 317 arranged on either side of the pressure chamber 313 exceeds the tolerance range. This makes it possible to ensure appropriate ejection characteristics of ink from the ejection holes 315 in each individual flow path 31.

In this embodiment, the flow resistance of the second throttling section 317 is preferably smaller than the flow resistance of the first throttling section 316 within a range of 15%. That is, when the flow resistance of the first throttling section 316 is R1 and the flow resistance of the second throttling section 317 is R2, R1 and R2 are set to satisfy 0.85R1≦R2<R1. This makes it possible to ensure appropriate ejection characteristics of ink from the ejection hole 315 while making it easier for ink not ejected from the ejection hole 315 to flow through the second throttling section 317 to the second common flow path 33. In this case, by making the flow cross-sectional area of the second throttling section 317 larger than the flow cross-sectional area of the first throttling section 316, the flow resistance of the second throttling section 317 can be made smaller than the flow resistance of the first throttling section 316.

When ink is circulating through the head body 21 in response to the driving of the pump 63 of the circulation unit 6, if the displacement element 51 arranged above the pressure chamber 313 of each individual flow path 31 is driven, a portion of the ink supplied to the pressure chamber 313 through the first throttle section 316 from the flow path of the supply system including the supply flow path 41 and the first common flow path 32 is ejected from the ejection hole 315. At this time, if the flow rate of the ink ejected from the ejection hole 315 of each individual flow path 31 is large and exceeds a predetermined value, ink may flow back from the flow path of the recovery system including the second common flow path 33 and the recovery flow path 42 to each individual flow path 31 through the second throttle section 317. Such backflow of ink to each individual flow path 31 will be described with reference to the graph of flow rate change shown in FIG. 10.

When the pump 63 of the circulation unit 6 is driven, in the head body 21, ink circulates at a preset circulation flow rate QA through the supply flow path 41 and the first common flow path 32, which are the flow paths of the supply system, each individual flow path 31, and the second common flow path 33 and the recovery flow path 42, which are the flow paths of the recovery system. When the displacement element 51 is driven while the ink is circulating at the circulation flow rate QA, the ink supplied to the pressure chamber 313 from the supply flow path 41 and the first common flow path 32 of the supply system through the first throttling section 316 of each individual flow path 31 is ejected from the ejection hole 315 at an ejection flow rate based on the print data, and the ink not ejected from the ejection hole 315 flows through the second throttling section 317 to the second common flow path 33 and the recovery flow path 42 of the recovery system and is recovered.

When ink ejection from the ejection hole 315 begins in response to the driving of the displacement element 51, the inflow flow rate of ink flowing in from the inlet 411 of the supply flow path 41 gradually increases from the circulation flow rate QA until it reaches the supply system saturation flow rate QS1, which indicates the saturation flow rate of ink flowing in the supply flow path 41, the first common flow path 32, and the first throttle section 316 in that order. The inflow flow rate of ink flowing in from the inlet 411 of the supply flow path 41 is held constant at the supply system saturation flow rate QS1 while ink is being ejected from the ejection hole 315 at the ejection flow rate based on the print data. When ink ejection from the ejection hole 315 ends, the inflow flow rate of ink flowing in from the inlet 411 of the supply flow path 41 gradually decreases from the supply system saturation flow rate QS1 until it returns to the circulation flow rate QA.

On the other hand, when ink ejection from the ejection hole 315 begins in response to the drive of the displacement element 51, the flow rate of ink flowing out from the outlet 421 of the recovery flow path 42 gradually decreases from the circulation flow rate QA until it reaches the recovery system saturation flow rate QS2, which indicates the saturation flow rate of ink flowing through the second throttling section 317, the second common flow path 33, and the recovery flow path 42 in that order. The flow rate of ink flowing out from the outlet 421 of the recovery flow path 42 is kept constant at the recovery system saturation flow rate QS2 while ink is being ejected from the ejection hole 315 at the ejection flow rate based on the print data. When ink ejection from the ejection hole 315 ends, the flow rate of ink flowing out from the outlet 421 of the recovery flow path 42 gradually increases from the recovery system saturation flow rate QS2 until it returns to the circulation flow rate QA.

Here, the circulation flow rate QA when ink circulates through the head body 21 is preset so as to be able to regulate the retention of ink near the ejection holes 315 that open to the outside in the head body 21 in order to suppress an increase in the viscosity of the ink due to the evaporation of volatile components in the ink. Also, in the head body 21, a maximum ejection flow rate QB, which indicates the maximum allowable value of the ejection flow rate when ink is ejected from the ejection holes 315, is preset. The maximum ejection flow rate QB is set to a value, for example, greater than twice the circulation flow rate QA.

Furthermore, the flow path resistance R of each of the supply flow path 41 and the first common flow path 32 of the supply system, the first throttling section 316 and the second throttling section 317 of each individual flow path 31, and the second common flow path 33 and the recovery flow path 42 of the recovery system when the cross-sectional shape of the flow path is rectangular is calculated according to the following formula (1).

In formula (1), "a" represents the length of the long side of the rectangular cross section of the flow path, "b" represents the length of the short side of the rectangular cross section of the flow path, "L" represents the flow path length along the ink flow direction, and "v" represents the viscosity of the ink. Note that "X" in formula (1) is calculated according to the following formula (2).

In formula (2), "a" and "b" are the same as in formula (1), "π" represents the ratio of the circumference of a circle to its diameter, and "h" represents the damping constant.

As is clear from formula (1), the flow path resistance R of each of the supply flow path 41 and the first common flow path 32 of the supply system, the first throttling section 316 and the second throttling section 317 of each individual flow path 31, and the second common flow path 33 and the recovery flow path 42 of the recovery system can be adjusted by the flow path cross-sectional area and the flow path length. In this embodiment, the flow path resistance R of each flow path is adjusted by the flow path cross-sectional area of each flow path.

The supply system saturation flow rate QS1 during ink ejection when ink is ejected from the ejection hole 315 at the maximum ejection flow rate QB is calculated according to the following formula (3) using the circulation flow rate QA and the maximum ejection flow rate QB.

In formula (3), "RS1" represents the supply system combined flow path resistance indicating the combined flow path resistance of the first common flow path 32, the supply flow path 41, and the first throttling section 316, and "RS2" represents the recovery system combined flow path resistance indicating the combined flow path resistance of the second common flow path 33, the recovery flow path 42, and the second throttling section 317.

As is clear from formula (3), the supply system saturation flow rate QS1 is determined by the preset circulation flow rate QA and maximum discharge flow rate QB, the supply system combined flow path resistance RS1, and the recovery system combined flow path resistance RS2.

The recovery system saturation flow rate QS2 during ink ejection when ink is ejected from the ejection hole 315 at the maximum ejection flow rate QB is calculated according to the following formula (4) based on the supply system saturation flow rate QS1 and the maximum ejection flow rate QB.

The recovery system saturation flow rate QS2 is based on the supply system saturation flow rate QS1 and the maximum discharge flow rate QB, and is therefore determined by the preset circulation flow rate QA and maximum discharge flow rate QB, the supply system combined flow path resistance RS1, and the recovery system combined flow path resistance RS2, just like the supply system saturation flow rate QS1.

Assume that the maximum discharge flow rate QB is set to a value greater than twice the circulation flow rate QA, and the supply system combined flow path resistance RS1 and the recovery system combined flow path resistance RS2 are the same. In this case, from equations (3) and (4), the recovery system saturation flow rate QS2 falls below 0 (zero). For example, if the circulation flow rate QA is 20 ml/min and the maximum discharge flow rate QB is 100 ml/min, and the supply system combined flow path resistance RS1 and the recovery system combined flow path resistance RS2 are the same, from equation (3) the supply system saturation flow rate QS1 will be 70 ml/min, and from equation (4) the recovery system saturation flow rate QS2 will be -30 ml/min, and the recovery system saturation flow rate QS2 will fall below 0 (zero). When the recovery system saturation flow rate QS2 falls below 0 (zero), ink flows back from the recovery system flow paths, including the second common flow path 33 and the recovery flow path 42, through the second throttle section 317 into each individual flow path 31 while ink is being ejected from the ejection hole 315.

When ink flows back from the flow paths of the recovery system, including the second common flow path 33 and the recovery flow path 42, through the second narrowing section 317 to each individual flow path 31, the ink that flows back to each individual flow path 31 is ejected from the ejection hole 315, and the ejected ink lands on the workpiece W, which may degrade the quality of the image formed on the workpiece W. For example, if the first filter 311A and the second filter 412C are provided in the flow paths of the supply system, including the first common flow path 32 and the supply flow path 41, but no filter is provided in the flow paths of the recovery system, ink containing foreign matter, etc. will flow back from the flow paths of the recovery system through the second narrowing section 317 to each individual flow path 31. In this case, ink containing foreign matter, etc. will be ejected from the ejection hole 315, and the quality of the image of the workpiece W will degrade due to the foreign matter, etc.

In order to prevent ink from flowing back from the recovery system flow paths, including the second common flow path 33 and the recovery flow path 42, to each individual flow path 31 through the second throttling section 317 while ink is being ejected from the ejection hole 315, it is necessary to ensure that the recovery system saturation flow rate QS2, which is based on the supply system saturation flow rate QS1 and the maximum ejection flow rate QB, does not fall below 0 (zero) while ink is being ejected from the ejection hole 315, as shown in the following formula (5).

Therefore, in the liquid ejection head 2 according to this embodiment, the recovery system combined flow path resistance RS2, which indicates the combined flow path resistance of the second common flow path 33, the recovery flow path 42, and the second throttling section 317, is greater than the supply system combined flow path resistance RS1, which indicates the combined flow path resistance of the first common flow path 32, the supply flow path 41, and the first throttling section 316. In other words, the recovery system combined flow path resistance RS2, which indicates the combined flow path resistance of the recovery flow path 42, the second common flow path 33 connected to the recovery flow path 42, and the second throttling section 317 connected to the second common flow path 33, is greater than the supply system combined flow path resistance RS1, which indicates the combined flow path resistance of the supply flow path 41, the first common flow path 32 connected to the supply flow path 41, and the first throttling section 316 connected to the first common flow path 32. For example, when the circulation flow rate QA is 20 ml/min and the maximum ejection flow rate QB is 100 ml/min, it is assumed that the ratio of the supply system combined flow path resistance RS1 to the recovery system combined flow path resistance RS2 is 1:10. In this case, the supply system saturation flow rate QS1 is 110.9 ml/min according to formula (3), and the recovery system saturation flow rate QS2 is 10.9 ml/min according to formula (4). The recovery system saturation flow rate QS2 satisfies formula (5) and does not fall below 0 (zero).

Compared to when the supply system combined flow path resistance RS1 and the recovery system combined flow path resistance RS2 are the same, by making the recovery system combined flow path resistance RS2 larger than the supply system combined flow path resistance RS1, it is possible to reduce the flow rate change between the circulation flow rate QA and the recovery system saturation flow rate QS2 for the ink flow rate flowing out from the outlet 421 of the recovery flow path 42. This makes it possible to prevent the recovery system saturation flow rate QS2 for the ink flow rate flowing out from the outlet 421 from falling below 0 (zero), making it possible to prevent ink from flowing back from the flow paths of the recovery system, including the second common flow path 33 and the recovery flow path 42, through the second throttle section 317 to each individual flow path 31.

In order to reliably prevent ink from flowing back from the recovery system flow paths to each individual flow path 31 through the second throttle section 317, the recovery system combined flow path resistance RS2 should be set to a value greater than the supply system combined flow path resistance RS1 so as to satisfy the following formula (6) using the circulation flow rate QA and the maximum discharge flow rate QB, which are derived from formulas (3) and (5).

As described above, as is clear from formula (1), the flow path resistance R of each of the supply flow path 41 and first common flow path 32 of the supply system, the first throttling section 316 and the second throttling section 317 in each individual flow path 31, and the second common flow path 33 and the recovery flow path 42 of the recovery system can be adjusted by the flow path cross-sectional area of each flow path. Therefore, in this embodiment, the total flow path cross-sectional area of each of the second common flow path 33, the recovery flow path 42, and the second throttling section 317 is smaller than the total flow path cross-sectional area of each of the first common flow path 32, the supply flow path 41, and the first throttling section 316. This makes it possible to make the recovery system combined flow path resistance RS2 larger than the supply system combined flow path resistance RS1.

In this embodiment, the flow resistance R of the second common flow path 33 is greater than the flow resistance R of the first common flow path 32. For example, by making the flow path cross-sectional area of the second common flow path 33 smaller than the flow path cross-sectional area of the first common flow path 32, the flow path resistance R of the second common flow path 33 can be made greater than the flow path resistance R of the first common flow path 32. This makes it possible to set the recovery system combined flow path resistance RS2 and the supply system combined flow path resistance RS1 so that the recovery system combined flow path resistance RS2 is greater than the supply system combined flow path resistance RS1. This makes it possible to more reliably suppress the backflow of ink from the flow paths of the recovery system, including the second common flow path 33 and the recovery flow path 42, through the second narrowing portion 317 to each individual flow path 31.

In addition, in this embodiment, the flow path resistance R of the recovery flow path 42 is larger than the flow path resistance R of the supply flow path 41. Specifically, the flow path resistance R of the first recovery branch flow path 423A in the recovery branch flow path 423 of the recovery flow path 42 is larger than the flow path resistance R of the first supply branch flow path 413A in the supply branch flow path 413 of the supply flow path 41. For example, by making the flow path cross-sectional area of the first recovery branch flow path 423A smaller than the flow path cross-sectional area of the first supply branch flow path 413A, the flow path resistance R of the first recovery branch flow path 423A can be made larger than the flow path resistance R of the first supply branch flow path 413A. As a result, the recovery system combined flow path resistance RS2 and the supply system combined flow path resistance RS1 can be set so that the recovery system combined flow path resistance RS2 is larger than the supply system combined flow path resistance RS1. Therefore, it is possible to more reliably suppress the backflow of ink from the flow paths of the recovery system, including the second common flow path 33 and the recovery flow path 42, to each individual flow path 31 through the second narrowing portion 317.

In addition, in this embodiment, the flow path resistance R of the second common flow path 33 is greater than the flow path resistance R of the first common flow path 32, and the flow path resistance R of the recovery flow path 42 is greater than the flow path resistance R of the supply flow path 41. This makes it possible to set the recovery system combined flow path resistance RS2 and the supply system combined flow path resistance RS1 so that the recovery system combined flow path resistance RS2 is greater than the supply system combined flow path resistance RS1. This makes it possible to more reliably prevent ink from flowing back from the flow paths of the recovery system, including the second common flow path 33 and the recovery flow path 42, through the second narrowing portion 317 to each individual flow path 31.

Furthermore, in the circulation section 6 arranged outside the liquid ejection head 2, the flow path resistance of the external recovery flow path member 65 connected to the outlet 421 of the recovery flow path 42 may be set to a value greater than the flow path resistance of the external supply flow path member 64 connected to the inlet 411 of the supply flow path 41. In this case as well, it is possible to prevent ink from flowing back from the flow paths of the recovery system, including the second common flow path 33 and the recovery flow path 42, to each individual flow path 31 through the second throttle section 317.

The behavior of the flow rate change at the start of ink ejection from the ejection hole 315 for the ink inflow flow rate from the inlet 411 of the supply flow path 41 and the ink outflow flow rate from the outlet 421 of the recovery flow path 42 is determined by the pressure loss P shown in the following formula (7) and the damping ratio d shown in the following formula (8).

In equation (7), "R" represents the flow resistance of each flow path in the supply system and recovery system, and "U" represents the change in flow rate of the inflow and outflow.

In formula (8), "C" represents the compliance in each of the supply storage chamber 412 and the recovery storage chamber 422, "R" represents the flow path resistance of each flow path of the supply system and the recovery system, and "M" represents the inertance in each of the supply storage chamber 412 and the recovery storage chamber 422.

The compliance C in each of the supply storage chamber 412 and the recovery storage chamber 422 indicates the amount of volumetric displacement per unit pressure corresponding to the elastic deformation of the elastic film 43 that closes the supply external opening 412B of the supply storage chamber 412 and the recovery external opening 422B of the recovery storage chamber 422. Compliance C is defined as C = ΔV/Δp, where V is the volume of ink in the flow path and p is the pressure applied to the ink in the flow path. Inertance M in each of the supply storage chamber 412 and the recovery storage chamber 422 is defined as M = ρL/S, where ρ is the ink density, L is the flow path length along the ink flow direction, and S is the flow path cross-sectional area.

In this embodiment, since the recovery system combined flow path resistance RS2 is greater than the supply system combined flow path resistance RS1, according to formula (8), the recovery storage chamber 422 of the recovery system is more likely to damp than the supply storage chamber 412 of the supply system. Therefore, when ink starts to be ejected from the ejection hole 315, the ink in the supply storage chamber 412 of the supply system will experience greater pressure vibrations than the ink in the recovery storage chamber 422 of the recovery system.

Therefore, when the recovery system combined flow path resistance RS2 is greater than the supply system combined flow path resistance RS1, the compliance C of the supply storage chamber 412 is greater than the compliance C of the recovery storage chamber 422 so that the damping ratio d in the supply storage chamber 412 and the damping ratio d in the recovery storage chamber 422 are the same. In this case, the inertance M of the supply storage chamber 412 and the inertance M of the recovery storage chamber 422 are made the same.

The compliance C of the supply storage chamber 412 can be adjusted, for example, by the opening area of the supply external opening 412B in the supply storage chamber 412 that is blocked by the elastic film 43. Similarly, the compliance C of the recovery storage chamber 422 can be adjusted, for example, by the opening area of the recovery external opening 422B in the recovery storage chamber 422 that is blocked by the elastic film 43. Note that when a first elastic film that blocks the supply external opening 412B of the supply storage chamber 412 and a second elastic film that blocks the recovery external opening 422B of the recovery storage chamber 422 are arranged as the elastic film 43, the compliance C of each of the supply storage chamber 412 and the recovery storage chamber 422 may be adjusted by the Young's modulus related to the elastic deformation of each of the first elastic film and the second elastic film and the thickness of the elastic film 43.

By making the compliance C of the supply chamber 412 greater than the compliance C of the recovery chamber 422 so that the damping ratios d of the supply chamber 412 and the recovery chamber 422 are the same, the pressure vibrations of the ink in the supply chamber 412 and the recovery chamber 422 can be made the same when ink starts to be ejected from the ejection hole 315.

1. Printer (liquid ejection device)
Reference Signs List 2 Liquid ejection head 3 First flow path member 31 Individual flow path 311 One end 312 Other end 313 Pressurizing chamber 315 Discharge hole 316 First throttling section 317 Second throttling section 32 First common flow path 321 First opening 33 Second common flow path 331 Second opening 4 Second flow path member 41 Supply flow path 411 Inlet 412 Supply storage chamber 42 Recovery flow path 421 Outlet 422 Recovery storage chamber 43 Elastic film 5 Piezoelectric actuator substrate 51 Displacement element (pressurizing section)
6 Circulation section 61 Supply storage section 62 Recovery storage section 63 Pump 64 External supply flow path member 65 External recovery flow path member

Claims

a plurality of individual flow paths through which a liquid flows, each of which has one end, an other end, and an ejection hole disposed between the one end and the other end and ejecting the liquid;
a first common flow passage having a first opening and connected to the one end of each of the individual flow passages;
a second common flow passage having a second opening and connected to the other end of each of the individual flow passages;
a supply flow path having an inlet through which liquid flows in from the outside, the supply flow path being connected to the first opening of the first common flow path and supplying the liquid that has flowed in from the inlet to the first common flow path through the first opening;
a recovery flow path having an outlet through which liquid flows out to the outside, connected to the second opening of the second common flow path, and causing the liquid recovered from the second common flow path through the second opening to flow to the outlet,
each of the individual flow paths is provided between the one end and the other end so as to communicate with the discharge hole, and includes a pressurizing chamber in which a pressurizing unit that applies pressure is disposed, a first throttling portion that is provided between the one end and the pressurizing chamber and has a flow path resistance greater than that of the pressurizing chamber, and a second throttling portion that is provided between the other end and the pressurizing chamber and has a flow path resistance greater than that of the pressurizing chamber,
a combined flow path resistance of the second common flow path, the recovery flow path, and the second throttle portion is greater than a combined flow path resistance of the first common flow path, the supply flow path, and the first throttle portion.
The liquid ejection head according to claim 1, wherein the flow resistance of each of the first and second throttling sections is set so that the difference between the flow resistances falls within a predetermined tolerance range.
The liquid ejection head according to claim 2, wherein the flow resistance of the second throttling section is less than the flow resistance of the first throttling section by within 15%.
The liquid ejection head according to claim 1, wherein the flow resistance of the second common flow path is greater than the flow resistance of the first common flow path.
The liquid ejection head according to claim 1, wherein the flow resistance of the recovery flow path is greater than the flow resistance of the supply flow path.
The liquid ejection head according to claim 1, wherein the flow resistance of the second common flow path is greater than the flow resistance of the first common flow path, and the flow resistance of the recovery flow path is greater than the flow resistance of the supply flow path.
the supply flow path includes a supply storage chamber that is in communication with the inlet, is capable of storing the liquid that has flowed in from the inlet, and has a supply external opening that is open to the outside;
the recovery flow passage includes a recovery storage chamber that is in communication with the outlet, is capable of storing the liquid flowing out from the outlet, and has a recovery external opening that is open to the outside;
The supply external opening of the supply storage chamber is closed by a first elastic film that is elastically deformable,
the recovery external opening of the recovery storage chamber is closed by a second elastic film that is elastically deformable;
A liquid ejection head as described in claim 1, wherein compliance indicating the amount of volumetric displacement per unit pressure corresponding to the elastic deformation of the first elastic film in the supply storage chamber is greater than the compliance corresponding to the elastic deformation of the second elastic film in the recovery storage chamber.
The liquid ejection head according to claim 7, wherein the first elastic film and the second elastic film are integrally formed.
a plurality of individual flow paths through which a liquid flows, each of which has one end, an other end, and an ejection hole disposed between the one end and the other end and ejecting the liquid;
a first common flow passage having a first opening and connected to the one end of each of the individual flow passages;
a second common flow passage having a second opening and connected to the other end of each of the individual flow passages;
a supply flow path having an inlet through which liquid flows in from the outside, the supply flow path being connected to the first opening of the first common flow path and supplying the liquid that has flowed in from the inlet to the first common flow path through the first opening;
a recovery flow path having an outlet through which liquid flows out to the outside, connected to the second opening of the second common flow path, and causing the liquid recovered from the second common flow path through the second opening to flow to the outlet,
each of the individual flow paths is provided between the one end and the other end so as to communicate with the discharge hole, and includes a pressurizing chamber in which a pressurizing unit that applies pressure is disposed, a first throttling portion that is provided between the one end and the pressurizing chamber and has a flow path resistance greater than that of the pressurizing chamber, and a second throttling portion that is provided between the other end and the pressurizing chamber and has a flow path resistance greater than that of the pressurizing chamber,
A liquid ejection head, wherein a total area of the cross-sectional areas of the second common flow path, the recovery flow path, and the second throttling portion is smaller than a total area of the cross-sectional areas of the first common flow path, the supply flow path, and the first throttling portion.
A liquid ejection head according to any one of claims 1 to 9,
a circulation unit connected to the inlet and the outlet of the liquid ejection head, and circulating liquid through the liquid ejection head.
The circulation section includes:
a supply reservoir configured to store liquid to be supplied to the inlet of the liquid ejection head;
a recovery reservoir that accumulates the liquid discharged from the outlet of the liquid ejection head;
a pump for pumping liquid from the return reservoir to the supply reservoir;
an external supply flow path member that connects the supply storage portion and the inlet and forms a flow path through which the liquid stored in the supply storage portion flows to the inlet;
an external recovery flow path member that connects the recovery reservoir and the outlet and forms a flow path through which the liquid discharged from the outlet flows to the recovery reservoir,
The liquid ejection device according to claim 10 , wherein a flow resistance of the external recovery flow path member is greater than a flow resistance of the external supply flow path member.